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Author Topic: 4L80e transmission swap  (Read 1660 times)
critter
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« on: January 02, 2010, 08:36:48 AM »

It has begun. I'm updating a thread on our club web site with details so, in the interest of not typing it all twice, here's a link.

http://tinyurl.com/yjza523
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LeighP
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« Reply #1 on: January 02, 2010, 07:44:53 PM »

Nice Chris....using the Shiftworks kit for the shifter detents?

I see the HPP is currently running a three part article on a 4L85E swap into a 74 T/A....very similiar to your points. It seems they gave up on modifying the original crossmember after they cut it out like yours....and fabricated a new crossmember altogether. You might want to use the trans mount tab off a later TH350 crossmember, I believe the 4L80E/85E use a single bolt style rear mount.

Interesting to see it all come together.
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Regards,
Leigh

Sydney, Australia
Former Firebirds -
1971 Pontiac Firebird 455
1977 Pontiac Trans Am
1976 Pontiac Trans Am
1967 Pontiac Firebird 400 convertible
1967 Pontiac Firebird 400 coupe

critter
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« Reply #2 on: January 02, 2010, 08:03:59 PM »

Yes, I'd offered my swap to Tom as a story setup but he already had that on in the pipe. That's where I got the pilot bearing information from that didn't work for me. I'm not sure what the difference is but I've called Tom and left a message. I want to understand it.

That crossmember thing is interesting. I have a 2 bolt mount for the TH400 that bolted right up to the 4L80e despite all the TH350 stuff I've heard. Go figure. Until we get that drive shaft I won't hazard a guess on what we'll end up with. Pinion angle can be critical.
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LeighP
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« Reply #3 on: January 03, 2010, 05:02:41 AM »

Probably the converter you're using has been set up for a Pontiac?...the one in the story that needs the pilot bushing is a GMPP lock up converter supplied with the 4L85E
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Regards,
Leigh

Sydney, Australia
Former Firebirds -
1971 Pontiac Firebird 455
1977 Pontiac Trans Am
1976 Pontiac Trans Am
1967 Pontiac Firebird 400 convertible
1967 Pontiac Firebird 400 coupe

76LQ9TA
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« Reply #4 on: January 04, 2010, 09:08:39 AM »

Does the fitting in the trans case for the rear cooling line have the extension on it?  It is needed to help lube the planetaries.  I didn't see it mentioned in your write up.  Sonnax carries this part.  I used the stock 2004 2wd 2500HD trans cooling lines and modified them at the radiator.  For the crossmember I cut off the stock mounting tab and welded it on the opposite side.
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81 LQ9 4L80E Trans Am
Two 79 400 4 speed TATA's
96 DCM Impala SS
Aaron91RS
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« Reply #5 on: January 04, 2010, 11:08:30 AM »


Sweet!
i'm doing a similiar thing(replacing a th400 with a 4l80e, although different engine.)
I took mine all apart in my basement first to add a transgo HD2 kit and fix some weak parts and see which of the 3 tail shafts I had so I got the right yoke.


Quote
Does the fitting in the trans case for the rear cooling line have the extension on it?
He's got an early year 4l80e with both cooler lines up front.
« Last Edit: January 04, 2010, 11:10:28 AM by Aaron91RS » Logged


80-Y84 WS6 SE LS1/4L80e
82 C3 LS1/4l60e
91RS-LS1/T56

www.fquick.com/aaron91rs
critter
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« Reply #6 on: January 04, 2010, 04:48:22 PM »

What he said regarding the cooler lines. This is a 1997 date tag but a GM Goodwrench replacement transmission that was pulled from a Suburban that was parted out. Both ports are up front.

Leigh, your explination was as good as any I've heard so far. We'll go with it. Smile
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Thomasmoto
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« Reply #7 on: January 04, 2010, 09:09:06 PM »

I'm also considering a OD install on my 79. What is the horsepower/torque limits of the 4L80E?  Do ya'll think this is better than using a T400 and a Gear Vendor unit? I'd really like to use a trans-brake. Is there a trans-brake of any of the Auto-OD units?
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David Thomas
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« Reply #8 on: January 04, 2010, 09:36:58 PM »

Most folks say a 4L80e will take 500/500 HP/torque.

Gear Vendors is good but when I bought one and tried to fit it I found that you needed to cut the main reinforcing crossmember through the center of the unibody had to be cut and a plate rewelded to replace  it. I was unwilling to do that for two reasons. First, my car is a Super Duty and that kind of major surgery was unthinkable. Second, I questioned whether I was compromising the structural integrity of the car doing it.
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